Method and system for detection of nitrogenous explosives by using nuclear resonance absorption

Abstract

A method for the detection of a nitrogenous explosive material in an object is provided which makes use of nuclear resonance absorption. The object to be tested is placed between a 9.17 MeV γ-rays source and an γ-rays detector holding a nitrogen medium. The total and the non-resonant attenuation of the γ-rays flux is read by the detector and fed into a recorder. From the measured attenuation the net non-resonant attenuation is calculated and the amount of a nitrogenous explosive present in the object is determined therefrom. Also provided by the invention is a system for detecting a nitrogenous explosive in an object.

What is claimed is: 
     
       1. A method for the detection of a nitrogenous explosive material in an object, comprising: (i) placing on one side of the object a source for 9.17 MeV γ-rays adapted to produce a desired photon flux (emitted photon flux);   (ii) placing on the opposite side of the object a γ-ray detector or array of detectors with a nitrogen rich detection medium;   (iii) scanning the object with a γ-ray beam from said source;   (iv) reading from said γ-ray detector or array of detectors the total and the non-resonant attenuations of the incident photon flux; and   (v) deriving from said attenuations the net resonant attenuation and the spatial distribution thereof.   
     
     
       2. A method according to claim 1 comprising interpreting the said net resonant attenuation to derive a quantitative reading of any detected nitrogen. 
     
     
       3. A system for the detection of a nitrogenous explosive material in an object, comprising: (i) a source for 9.17 MeV γ-rays;   (ii) a γ-ray detector with a nitrogen-rich detection medium and adapted to show modulations of the detected photon flux;   (iii) holder means for holding an inspected object so as to intersect the γ-rays from said source for 9.17 MeV γ-rays; and   (iv) means for scanning the inspected object with the γ-rays emitted by said source for 9.17 MeV γ-rays.   
     
     
       4. A system according to claim 3 in which said holder means are movable whereby an inspected object is scanned by the γ-rays. 
     
     
       5. A system according to claim 4, wherein said holder means is a conveyor belt adapted to move a succession of objects for inspection across the γ-rays. 
     
     
       6. A system according to claim 3 in which the γ-ray source and detector are movable synchronically whereby an inspected object is scanned by the γ-rays. 
     
     
       7. A system according to claim 3, comprising processor means for continuously comparing the detected photon flux with the emitted photon flux. 
     
     
       8. A system according to claim 7, wherein said processor means are adapted to interpret any flux modulations obtained by scanning an object.